1. Technical Field
The present invention pertains to communication systems. In particular, the present invention pertains to a communication system employing link-based flooding schemes for transmission of routing control information (e.g., to synchronize routing databases, facilitate message transmissions, etc.) with reduced communication protocol overhead traffic.
2. Discussion of Related Art
Generally, wireless networks may be arranged in a two-tier architecture similar to that of conventional cellular telephone systems. The first tier typically includes clusters or cells each including a plurality of communication nodes or cluster members. One node within each cluster is designated as a cluster head or base station. The second tier includes a backbone network formed of the cluster head nodes to enable communications between different clusters (e.g., for data transmitted over greater distances). The formation of clusters and designation of cluster head nodes is generally performed dynamically and in accordance with an intranet protocol (e.g., a protocol for communications within the two-tier network) that further performs routing functions within the network. In order to facilitate internet routing or routing between the two-tier and other external networks (e.g., the Internet), a modified version of the conventional Open Shortest Path First (OSPF) Protocol is employed. The OSPF protocol is basically a routing protocol employed for Internet Protocol (IP) type networks, while the modified protocol or Radio Open Shortest Path First (ROSPF) protocol is similar to OSPF, but is adapted for use with radio or wireless networks. For examples of implementation of the OSPF Protocol, reference is made to RFC 1583, Moy, xe2x80x9cOSPF Version 2,xe2x80x9d March 1994, the disclosure of which is incorporated herein by reference in its entirety.
The intranet protocol is preferably a link-state type of routing protocol that is implemented on the backbone network. The cluster head nodes each include a database that is synchronized with other cluster head node databases by transference or flooding of Link-State Advertisement (LSA) packets in accordance with the protocol. These databases include information enabling the cluster head nodes to determine appropriate paths for routing messages through the network, while the LSA packets provide information to update the databases. Since the two-tier network is not a broadcast type network, LSA and other routing control packets are sent by a cluster head node as point-to-point messages to each of its cluster head neighbors.
The above-described technique for transmitting intranet protocol LSA and other routing control packets on a network suffers from several disadvantages. In particular, the intranet and ROSPF protocols each generate control traffic to maintain a functional network where the amount of control traffic increases with network size. With respect to the intranet protocol, the amount of overhead traffic depends on the average quantity of neighboring cluster head nodes and the size of the backbone network. In fact, the amount of intranet protocol overhead traffic increases at a significantly greater rate than network capacity as the size of the backbone network increases, thereby degrading network performance. Although the intranet protocol introduces additional overhead in initializing neighbors, the predominant portion of the overhead is attributed to the flooding or transmission of LSA and other routing control packets. Since network performance is affected by the control traffic, the network becomes unsuitable to transport user traffic or maintain a functioning state in the event that the control traffic approaches or exceeds the network capacity. This typically occurs when the size of the network is greater than approximately one-hundred fifty nodes where the backbone network size is proportional to the size of the network. Accordingly, since networks may employ on the order of approximately one-thousand nodes, the increased overhead limits network performance of small-scale networks and restricts deployment of the protocol for large-scale networks.
The present invention overcomes the aforementioned problems and achieves transmission of LSA and other routing control packets with a reduced rate of overhead increase in relation to backbone network and overall network size. This is accomplished by selectively controlling enablement of control links that facilitate transfer of routing control information between cluster head nodes within the backbone network. The present invention minimizes the impact of protocol overhead on network throughput, and permits the protocol to be utilized on large-scale wireless networks. Thus, networks may employ the protocol, while scaling to a greater size.
Accordingly, it is an object of the present invention to reduce the rate of overhead of a communication routing protocol and enable employment of the protocol with large-scale type networks.
It is another object of the present invention to selectively control enablement of control links for transference of routing control information between network nodes to reduce communication protocol overhead traffic and enhance communication network throughput.
Yet another object of the present invention is to synchronize routing databases of communication network nodes in a manner that minimally affects network throughput.
The aforesaid objects may be achieved individually and/or in combination, and it is not intended that the present invention be construed as requiring two or more of the objects to be combined unless expressly required by the claims attached hereto.
According to the present invention, Link-State Advertisement (LSA) and other routing control packets are transmitted within a wireless communication system or network via selective enablement of control links for transference of the packets between network nodes. Specifically, an exemplary wireless network includes a plurality of nodes arranged into clusters with each cluster having cluster member nodes and a designated cluster head node. The nodes communicate with each other via an intranet protocol, while the network may communicate with other external networks in accordance with an internetworking protocol (e.g., a modified version of the conventional Open Shortest Path First (OSPF) routing protocol, or a Radio Open Shortest Path First (ROSPF) protocol). A database within each network head node contains link information for that node. The LSA packets contain information to update the head node databases, while other routing control packets generally contain various routing information for network nodes to facilitate message transmissions. The routing control packets are transmitted to each head node to control routing functions and enable each database to maintain current information. In order to reduce overhead traffic due to transmission of numerous LSA and other routing control packets, the present invention selectively controls enablement of control links (e.g., links that transport routing control information) to transmit the LSA and other routing control packets to head nodes within the network. In other words, the present invention selectively reduces the quantity of control links between head nodes to transmit the LSA and other routing control packets with reduced protocol overhead traffic, thereby permitting the network to utilize link-state based protocols effectively (e.g., with minimal impact on network throughput) while expanding to larger scales.
The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, particularly when taken in conjunction with the accompanying drawings wherein like reference numerals in the various figures are utilized to designate like components.